Rollup merge of #136239 - folkertdev:show-supported-register-classes, r=SparrowLii,jieyouxu

show supported register classes in error message

a simple diagnostic change that shows the supported register classes when an invalid one is found.

This information can be hard to find (especially for unstable targets), and this message now gives at least something to try or search for. I've followed the pattern for invalid clobber ABIs.

`@rustbot` label +A-inline-assembly

4 files changed, 15 insertions, 8 deletions

diff --git a/compiler/rustc_ast_lowering/messages.ftl b/compiler/rustc_ast_lowering/messages.ftl
index f96c9fe8e32..1b91c33742d 100644
--- a/compiler/rustc_ast_lowering/messages.ftl
+++ b/compiler/rustc_ast_lowering/messages.ftl
@@ -112,7 +112,8 @@ ast_lowering_invalid_register =
     invalid register `{$reg}`: {$error}
 
 ast_lowering_invalid_register_class =
-    invalid register class `{$reg_class}`: {$error}
+    invalid register class `{$reg_class}`: unknown register class
+    .note = the following register classes are supported on this target: {$supported_register_classes}
 
 ast_lowering_match_arm_with_no_body =
     `match` arm with no body
diff --git a/compiler/rustc_ast_lowering/src/asm.rs b/compiler/rustc_ast_lowering/src/asm.rs
index 2f1f1269ece..96c230ec243 100644
--- a/compiler/rustc_ast_lowering/src/asm.rs
+++ b/compiler/rustc_ast_lowering/src/asm.rs
@@ -152,11 +152,16 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     InlineAsmRegOrRegClass::RegClass(reg_class) => {
                         asm::InlineAsmRegOrRegClass::RegClass(if let Some(asm_arch) = asm_arch {
                             asm::InlineAsmRegClass::parse(asm_arch, reg_class).unwrap_or_else(
-                                |error| {
+                                |supported_register_classes| {
+                                    let mut register_classes =
+                                        format!("`{}`", supported_register_classes[0]);
+                                    for m in &supported_register_classes[1..] {
+                                        let _ = write!(register_classes, ", `{m}`");
+                                    }
                                     self.dcx().emit_err(InvalidRegisterClass {
                                         op_span: *op_sp,
                                         reg_class,
-                                        error,
+                                        supported_register_classes: register_classes,
                                     });
                                     asm::InlineAsmRegClass::Err
                                 },
diff --git a/compiler/rustc_ast_lowering/src/errors.rs b/compiler/rustc_ast_lowering/src/errors.rs
index 9f69387b7b7..f31e2db051d 100644
--- a/compiler/rustc_ast_lowering/src/errors.rs
+++ b/compiler/rustc_ast_lowering/src/errors.rs
@@ -197,12 +197,13 @@ pub(crate) struct InvalidRegister<'a> {
 }
 
 #[derive(Diagnostic)]
+#[note]
 #[diag(ast_lowering_invalid_register_class)]
-pub(crate) struct InvalidRegisterClass<'a> {
+pub(crate) struct InvalidRegisterClass {
     #[primary_span]
     pub op_span: Span,
     pub reg_class: Symbol,
-    pub error: &'a str,
+    pub supported_register_classes: String,
 }
 
 #[derive(Diagnostic)]
diff --git a/compiler/rustc_target/src/asm/mod.rs b/compiler/rustc_target/src/asm/mod.rs
index 0a4ffb15219..9f791603c72 100644
--- a/compiler/rustc_target/src/asm/mod.rs
+++ b/compiler/rustc_target/src/asm/mod.rs
@@ -39,12 +39,12 @@ macro_rules! def_reg_class {
                 }
             }
 
-            pub fn parse(name: rustc_span::Symbol) -> Result<Self, &'static str> {
+            pub fn parse(name: rustc_span::Symbol) -> Result<Self, &'static [rustc_span::Symbol]> {
                 match name {
                     $(
                         rustc_span::sym::$class => Ok(Self::$class),
                     )*
-                    _ => Err("unknown register class"),
+                    _ => Err(&[$(rustc_span::sym::$class),*]),
                 }
             }
         }
@@ -635,7 +635,7 @@ impl InlineAsmRegClass {
         }
     }
 
-    pub fn parse(arch: InlineAsmArch, name: Symbol) -> Result<Self, &'static str> {
+    pub fn parse(arch: InlineAsmArch, name: Symbol) -> Result<Self, &'static [rustc_span::Symbol]> {
         Ok(match arch {
             InlineAsmArch::X86 | InlineAsmArch::X86_64 => {
                 Self::X86(X86InlineAsmRegClass::parse(name)?)